1. Field of the Invention
This invention relates to a voltage measuring device, which is particularly adapted for measuring high-voltages on encapsulated switching installations containing an inner conductor within a grounded metallic outer tube.
2. Description of the Prior Art
Previous methods for monitoring the voltage of high-voltage switching installations generally employed voltage transformers. A typical system is described in Deutsche Auslegungschrift No. 1,807,997. There a high-voltage system is described which employs a voltage transformer where the high voltage coil is located inside an insulating body, with core and the coils of the transformer located in a hermetically sealed, pressurized tank. The tank is filled with insulating gas and is secured to the metallic outer tube of the switching installation by a suitably flanged, gas-tight connection. The principal mode of operation for the transformer type measuring device is, of course, essentially inductive.
A voltage transformer of the type described in Deutsche Auslegungschrift No. 807,997 is only suitable for voltage ratings below a certain level. Higher voltages would require transformer designs which would need too much space. Split iron core transformers, alternately, although possibly handling the higher voltages, are relatively poor performing devices. Further, transformers for higher voltage rating installations become expensive when they must be designed to be made surge proof and free of partial discharge. A voltage transformer for completely insulated, metal clad high-voltage switching installations is described in Deutsche Offenlegungsschrift No. 2,125,297.
It is therefore a primary object of this invention to provide a voltage measuring device for application in high-voltage switching installations which is relatively simple in construction and consequently favorably cost.